Although stacking disorder in kaolinite was extensively investigated for a long time, its real structure has not been understood sufficiently. Recently high-resolution transmission electron microscopy (HRTEM) studies of kaolinite were reported with sufficient resolution to determine the origin of the stacking disorder directly. Most common stacking faults in kaolinite are disorder of the alternative layer displacement, t_1 (approximately -a/3) and t_2 (a/6-b/6), between adjacent layers. The two layer displacements are related to each other by the pseudo-mirror plane passing the octahedral vacant site in the kaolinite unit layer. Furthermore, this type of disorder can occur as (1) isolated stacking faults (for instance, insertion of t_2 in the ordered matrix with t_1) as well as (2) interstratifications of packets in which the layer displacement is ordered. These two occurrence modes of the t_1/t_2 disorder probably reflect the growth process of kaolinite. Disorder by displacement of the octahedral vacancy sites in the dioctahedral 1:1 layer and/or layer rotation, is another stacking disorder found in kaolinite of sedimentary origin.

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Two new species of F-mica, fluorokinoshitalite (BaMg_3Al_2Si_2O_<10>F_2) and fluorotetraferriphlogopite (KMg_3Fe^<3+>Si_3O_<10>F_2) occur in Bayan Obo, Inner Mongolia, China. They form subhedral to euhedral platy crystals in metamorphosed carbonate rocks. They are associated with phlogopite, yangzhumingite, and rare earth minerals such as bastnasite-(Ce), cordylite-(Ce), monazite-(Ce), fluorbritholite-(Ce) and huanghoite-(Ce). Fluorokinoshitalite is transparent and colorless with white streak and pearly luster. Cleavage is perfect on {001}. The calculated density is 3.235g cm^<-3>. Fluorotetraferriphlogopite is brown in color with white to pale brown streak. It is transparent showing pearly luster and perfect cleavage on {001}. The hardness is 3-4 on the Mohs scale. The calculated density is 2.966g cm^<-3>. This mineral is optically biaxial (-) with n=1.576 (min.)-1.582 (max.). It shows reverse pleochroism (Z'=colorless, X'=light brown). Electron microprobe analyses with SIMS for Li gave empirical formulae (based on 12 anions); (Ba_<0.56>Na_<0.25>K_<0.06>)(Mg_<2.76>Fe^<2+>_<0.14>Ti_<0.01>) (Si_<2.73>Al_<1.15>Fe^<3+>_<0.12>)O_<10>[F_<1.72>(OH)_<0.28>] and (K_<0.94>Na_<0.02>Ba_<0.01>)(Mg_<2.62>Li_<0.15>Fe^<+2>_<0.14>_Mn_<0.01>)(Si_<3.33>Fe^<3+>_<0.66>Al_<0.01>)O_<10>[F_<1.65>(OH)_<0.35>] for fluorokinoshitalite and fluorotetraferriphlogopite, respectively. The lattice parameters were refined in the monoclinic system (C2/m) with the XRD data obtained with an IP-Gandolfi camera as; a=5.3161 (11), b=9.2082(15), c=10.044(2) Å, β=100.158(18)°, V=483.97(17) Å^3 (fluorokinoshitalite) and a=5.325(3), b=9.217(5), c=10.192(7) Å, β=100.03(5)°, V=492.6(5) Å^3 (fluorotetraferriphlogopite).

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A mechanism of shape transformation from spheres to tubes in halloysite is proposed from the standpoint of curvature elasticity theory, using the size and morphological data of samples separated from chronological series of tephras in Hachijo Island. Transmission electron microscopic observations indicated that when the diameters of halloysite particles exceeded about 200nm, the shape showed prominent deviation from spherical to tubular and/or partially curled platy ones. This fact leads to that the spherical halloysite with 200nm in diameter is subjected to the curvature elastic energy of about 9kJ/m^2 due to the anti-bending of layers, which is an estimate using approximately the elastic constants of kaolinite and taking into account a preferable curvature for a single layer of halloysite. The curvature elastic energy acts as a driving force for the shape transformation. In reality irreversible dehydration process plays a trigger to transform such flustrated spherical halloysites to more stable shapes such as tubular ones.

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Microbes can significantly affect the dissolution rates of silicate minerals on the earth's surface environments. However, there is little information about molecular-level mechanism for enhancement of the dissooution rates by bacterial interaction. To evaluate the effects of bacteria on dissolution rates and to elucidate the molecular-level mechanism, experiments on dissolution of kaolinite in bacterial systems containing Pseudomonas fluorescens were performed in this study. The dissolution experiments were conducted using the batch reactors containing 0.2g of kaolinite and 100ml of 10mM NaCl solution with 10^5 to 10^9 cells/ml of P. fluorescens at 25℃ for up to 20 days. The results indicated that the dissolution rates of kaolinite increased by 1.6 to 10.4 times progressively with increasing bacterial concentrations from 10^5 to 10^9 cells/ml, respectively, relative to the bacteria-free control. The concentrations of dissolved Al ions also increased up to approximately log (IAP/K)=1.7 for saturation indices with respect to gibbsite. The analysis of dissolved organic molecules in the solutions revealed that significant amounts of proteins were released from the bacterial cells along with less or trace amounts of polysaccharides, nucleic acids, and organic acids. Thus, these extracellular organic molecules consisting mainly of proteins are likely to contribute to the enhancement of kaolinite dissolution by electrostatic interaction with the kaolinite surfaces and also by the complxation with the dissolved Al ions.

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Mineralogy of Asian dust collected in Fukuoka, Southwest Japan, was investigated using X-ray diffraction (XRD) and scanning/transmission electron microscopy (SEM/TEM) in detail. The dust consisted of only silicates; quartz, albite, orthoclase, amphibole and phyllosilicates (muscovite/illite, biotite, chlorite, kaolin group minerals and smectite). This mineral composition for silicates is very close to that of a certified reference specimen for Asian dust (CJ-1) which was collected from the loess plateau in China. However, carbonate minerals abundant in CJ-1 are missing in Fukuoka dust. Probably the carbonate and other water-soluble minerals were dissolved by rain or during sample collection using water. Observation and X-ray chemical analysis in SEM revealed their morphologies and chemical compositions. Amphibole, biotite and chlorite are major Fe-bearing minerals in the dust. Among them, fine chlorite particles may be a good Fe-supplier for microorganism living in the shallow area of the ocean.

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The high arsenic content in groundwaters of Kandal province, Cambodia has threatened about 1 million people with tens of them being at risk to arsenicosis. In this context, this study aims to investigate the removal of arsenic from Kandal groundwater by utilizing naturally available laterite from Kampong Cham province in order to obtain safe drinking waters for the people. The laterite samples were characterized with XRD, XRF, zeta potential analyzer, and surface area analyzer. Batch adsorption experiment of As(V) onto laterite was conducted under ambient temperature as a function of adsorbent dose, contact time, initial As concentration, solution pH, and coexisting phosphate concentration. Surface complexation modeling (SCM) was also performed in order to interpret the experimental results. The experimental results showed that 12.5g/L laterite could reduce arsenic to a level below the Cambodian guideline (50μg/L) within 40 minutes of contact time at neutral pH. The presence of phosphate in groundwater was insignificant in the decrease in arsenic removal. The results of SCM coupled with the experimental data indicate that most of adsorption behavior of arsenic onto the laterite such as dose, pH and phosphate effects would be attributed to iron minerals rather than other constituent minerals (i.e. quartz and kaolinite) in the laterite. Moreover, the minimum dose of laterite to completely adsorb 1.5mg/L arsenic was only 〜0.13g/L. This implies that only 1kg laterite is needed per year if 19.8 liters of water is required per day by a small family in Kandal province. Hence, the field applicability and availability of laterite in Kampong Cham must be considered to remove arsenic from groundwaters for the residents of Kandal province.

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Organic and inorganic complexes are formed by the intercalation of ethylene glycol and glycerol into the interlayer of montmorillonite. Glycerol and ethylene glycol have the molecular formula C_2H_6O_2 and C_3H_8O_3, respectively, and the general formula is C_nH_<2(n+1)>O_n. This formula represents a sugar alcohol group: erythritol for n=4, xylitol for n=5, sorbitol for n=6, and so on. Complexes were produced by a wet process, in which erythritol, xylitol and sorbitol solutions, and montmorillonite, were mixed to a paste; and by a dry process, in which montmorillonite and erythritol, xylitol and sorbitol, in the solid state, were mixed by automatic agate mortar. X-ray diffraction, FT-IR and X-ray photoelectron spectroscopy analyses of the resulting complexes showed that erythritol, xylitol and sorbitol were intercalated into the interlayer of montmorillonite in both wet and dry processes. The resulting complexes also showed an increase in the basal spacing with increasing n (or molecular weight or carbon chains). The difference between the wet and dry processes lies in the d-spacing in each montmorillonite-sugar alcohol system. The d-spacing of the complexes formed by the wet intercalation process were about 0.4nm larger than those formed by the dry intercalation process. This is the length of the longest part of the water molecule. In the wet process, the sugar alcohols were intercalated with water molecules, and the montmorillonite swelled, while it expanded in the dry process.

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